We are completing studies on the oxotremorine-stimulated rat colon as a model for peripheral nicotinic cholinergic receptors. In this system nicotine relaxes the muscle through an action on the intrinsic nerve plexuses. The nicotine evidently acts by releasing a smooth-muscle relaxant, which is not a catecholamine or adenosine, but which we have not been able to identify. The rank order of potencies for agonists and antagonists in this system support the characterization of the receptors as nicotinic cholinergic. We are completing studies on nicotine as a discriminative cue in rats, both by systemic and intracerebroventricular administration. The cueing effect is highly stereospecific, it is seen with other typical nicotinic cholinergic agonists (provided they have access to the brain), and it is blocked by nicotinic cholinergic antagonists. The work will be prepared for publication, including description of a new statistical method for analyzing drug discrimination results. Pilot studies on self-administration of nicotine by rats will continue. The novel feature of these experiments is the inclusion of a dummy bar, to control for increased motor activity due to nicotine, possibly resulting nonspecifically in bar-pressing behavior.